You should be able to do this with Custom Authentication, without the need for a beforeOperationRule.
In Custom Authentication, add a response mapping for the Token/SessionKey/etc. Name the Schema Attribute: accesstoken_CA. The Attribute Path would be equal to the JSON key for the Token/SessionKey/etc.
After you have saved that, go into your test connection, or other operation, and add a new header. Key should be the same as the Attribute Path from the previous step. Value would be equal to $application.accesstoken_CA$.
If you have that header in each operation, the custom authentication should be run prior to the operation being run.